Regex.Replace() - Is it possible to increment/decrement group values in-line?

Kevin Burt

Hello.

Does anyone know if it is possible to increment/decrement values in a Regex Group?

For example, the following code demonstrates capturing two groups called 'value1' and 'value2', and I would like to replace these value with (value1+1) and (value2-1) respectively.

string pattern = @"(?\d{1,2})/(?\d{1,2})";

string result = Regex.Replace(myString, patten, @"${value1}+1/${value2}-1");

I'm basically looking to manipulate multiple numeric values on a multi-line chunk of text.

Any advice would be much appreciated.

2 Replies

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Kevin Burt18y ago
Thanks Alan - that's exactly what I was looking for. I spent ages trawling through regex tutorials without any luck, so thanks again!
Alan18y ago
It's possible to do stuff like this using a MatchEvaluator. For example:

using System;
using System.Text.RegularExpressions;

class Program
{
    static void Main()
    {
      string myString = "5/7 and 4/19";
      string pattern = @"(?\d{1,2})/(?\d{1,2})";
      string result = Regex.Replace(myString, pattern,ReplaceEvaluator);
      Console.WriteLine(result);
    }

    static string ReplaceEvaluator(Match m)
    {
      int value1 = int.Parse(m.Groups["value1"].Value) + 1;
      int value2 = int.Parse(m.Groups["value2"].Value) - 1;
      return value1.ToString() + "/" + value2.ToString();
    }
}